The present invention relates generally to integrated circuits, and more particularly, to a one-pin low power crystal oscillator with fast start-up capability.
Modern clocking circuits in integrated circuits require stable frequency references (i.e., oscillators) with fast turn-on, small output noise, and low power consumption. Because of stringent frequency stability requirements, an external resonator with a high-quality factor (i.e., a quartz crystal) is typically employed in conjunction with active components in the integrated circuit for generating the reference oscillations. However, because the number of pins available in an integrated circuit for interfacing with other external circuits is limited, it is advantageous to use only one pin for connecting the resonator. Consequently, circuit implementations of oscillators that satisfy the foregoing requirements are challenging, especially in low-supply-voltage environments where the active devices (i.e., transistors) must operate with small headroom voltages.
Thus, there exists a need for a fast-starting, low-noise, and low-power, single-pin oscillator.